The renin-angiotensin system (RAS) can be interfered with by inhibition of the enzymes synthesizing angiotensins or by blocking the corresponding receptors at the effector sites. There are many marketed or investigation-stage agents which inhibit RAS activity, and many fall into two broad classes: the inhibitors of angiotensin-converting enzyme (ACE), whose approved names generally end in “-pril” or in the case of active metabolites “-prilat”, and antagonists at angiotensin receptors (more specifically, currently, the AT1 receptor) (Angiotensin II Antagonists), whose approved names generally end in “-sartan”. Also potentially of increasing importance may be a class of drugs known as neutral endopeptidase (NEP) inhibitors which will also have an ACE-inhibitory effect or the potential to reduce RAS activity and are therefore also known as NEP/ACE-inhibitors.
ACE inhibitors are well known in the art for their activity in inhibiting angiotensin converting enzyme, thereby blocking conversion of the decapeptide angiotensin I to angiotensin II. The principal pharmacological and clinical effects of ACE inhibitors arise from suppression of synthesis of angiotensin II. Angiotensin II is a potent pressor substance and, therefore, blood pressure lowering can result from inhibition of its biosynthesis, especially in animals and humans whose hypertension is angiotensin II related. ACE inhibitors are effective antihypertensive agents in a variety of animal models and are clinically useful for the treatment of hypertension in humans.
ACE inhibitors are also employed for the treatment of heart conditions such as hypertension and heart failure. It is known that at least some ACE inhibitors can improve (i.e., decrease) morbidity and mortality in patient populations with heart conditions, ie. patients with low ejection fraction (EF) or heart failure (HF), but their role in a broader population of high risk patients without ventricular dysfunction or HF is unknown.